The red line corresponds to the EU limit value of 125 μg/m3, EU Member States only.
The graph is based on the 99.18 percentiles of the daily mean concentration values for each Member State; the boxes
present the range of the 99.18 percentiles at all stations types (in μg/m3) with data officially reported by the EU Member
States and how they relate to the daily limit value set by EU legislation (marked by the red line).
The diagram indicates the lowest and highest observations, the means and the lower and upper quartiles. The lower quartile
splits the lowest 25 % of the data and the upper quartile splits the highest 25 % of the data.

Due to lack of detailed land cover data and/or rural ozone data Iceland and Norway are not included until 2006 and onwards. Switzerland have not been included in the analysis for the entire period 1996-2007 due to the same reasons. Turkey is not included in the analysis 1996-2008.

Forests are essential to our survival and well-being. Forests clean our air, our water, our soil and they regulate our climate, amongst many other things. Trees and forests are not always associated with urban landscapes. However, there too they provide invaluable, often invisible, services. Simply by acting as 'green oasis' in our concrete jungles, they offer recreation and health services for many European citizens.

Ground level ozone causes health problems, decreases crop yields and damages the environment. Ozone levels exceeding certain targets in Europe were less frequent in summer 2011 than in any year since monitoring started in 1997. However, the long-term objective was exceeded in all EU Member States and it is likely many of them will not meet the target value, applicable as of 2010.

Distribution of stations by thresholds of 90.41 percentile of daily PM10 concentrations for the year 2011. The figure is based on the 90.41 percentile of the PM10 daily concentrations, corresponding to the 36th highest PM10 concentration when data availability is 100% over the year.

In the air quality directive (2008/EC/50) the EU has set two limit values for sulphur dioxide (SO2) for the protection of human health: the SO2 hourly mean value may not exceed 350 micrograms per cubic metre (µg/m3) more than 24 times in a year and the SO2 daily mean value may not exceed 125 micrograms per cubic metre (µg/m3) more than 3 times in a year.